INTRODUCTION: Classical style in cross-country skiing (XCS) was the unique technique used until 1984, and was divided in three principal strides: Diagonal stride (DS), double poling (DP) and DP with kick (DPk). Even though the motion actions remain the same for the most part, several changes were found since the 90s due to different causes (Lindinger 2007). New equipment and materials, better ski track preparation, increases in the training methodology, and the specific use of upper body segments emphasized in skating enhanced the velocity and the performance in all types of races. Moreover, in classical races the use of different "gears" (DS, DP, DPk) are distributed in different fractions and steepness of the course. The aim of this work was to collect and to analyze the 3D kinematics of the typical strides in classic XCS performed by elite skiers, both male and female, engaged in recent World Cup races. METHODS: The data collection was performed in 2009 and 2010 during WC-XCS individual classical races. Dedicated software for video analysis (DLT method) was used (Baroni 1998). A total of 15 skiers (10 male and 5 female, ranking 1-30) were analyzed on 3 section races (flat, uphill~4°, uphill ~8°) where the athletes performed DP, DPk and DS strides. Correlational analysis between measured variables and skiing performance was conducted. RESULTS: A set of specific kinematics variables was measured for each athlete (tab. 1) and was reported as the mean value averaged on 2-3 movement cycles. Angles-vs.-angles plots were used to investigate individual coordination patterns. DISCUSSION/CONCLUSION: According to previous studies (Komi 1987, Bilodeau 1995, Smith 1996, Canclini 2000), we found that the faster skiers have longer cycle lengths in DS (r=0.57) and DPk (r=0.6). We did not find correlation between CoG Velocity and CL in DP. The kinematic patterns of shoulder, elbow and pole angles were found to be quite similar to literature data, but the values of the angle show no correlation with the CoG velocity. However it seems that the key point of the poling is the relative positioning of the upper/lower body limbs to each other and the sequential order of joint flexion/extension. Moreover the skiers adopted a different strategy for performing the poling with respect to the trunk, shoulder and elbow angular variations. The individual patterns of these joint strategies and additional biomechanical parameters are also discussed with reference to the potential significance for the optimization of the overall movement performance.
© Copyright 2012 Science and Skiing V. 5th International Congress on Science and Skiing, Dec. 14 - 19, 2010, St. Christoph am Arlberg. Published by Meyer & Meyer Sport (UK) Ltd.. All rights reserved.